# include <bits/stdc++.h>
using namespace std;
int i, t, n, sum;
int main() {
	t = 0, sum = 1;
	cin >> n;
	for(int i = 1; i <= n; i++) {
		sum *= i;
		while(sum % 10 == 0) {
			t++;
			sum /= 10;
		}
		sum %= 1000;
	}
	printf("%6d/n", t);
}
